Calibrate the camera
I have found that performing camera calibration helps fiducial recognition a lot. Realize that each robot has a slightly different camera and so the calibration file you find on the robot, conceivably, may be incorrect. When you get down to the wire, perform the calibration on your robot. It will help.
Making Fiducials
There are
Two types of Fiducials - Aruco and April Tags
How to recognize Fiducials
TF of Camera
TF of Fiducial
Static Transforms